The inability of visible light to penetrate far through biological tissue limits its use for
phototherapy and photodiagnosis of deep-tissue sites of disease. This is unfortunate because many visible
dyes are excellent
photosensitizers and photocatalysts that can induce a wide range of photochemical processes, including photogeneration of
reactive oxygen species. One potential
solution is to bring the light source closer to the site of disease by using a miniature implantable LED. With this goal in mind, we fabricated a wireless LED-based device (volume of 23 mm3) that is powered by RF energy and emits light with a wavelength of 573 nm. It has the capacity to excite the green absorbing
dye Rose Bengal, which is an efficient type II
photosensitizer. The wireless transfer of RF power is effective even when the device is buried in chicken breast and located 6 cm from the transmitting antenna. The combination of a wireless device as light source and
Rose Bengal as
photosensitizer was found to induce cell death of cultured HT-29 human colorectal
adenocarcinoma cells. Time-dependent generation of protruding bubbles was observed in the photoactivated cells suggesting cell death by light-induced pyroptosis and supporting evidence was gained by cell staining with the fluorescence probes
Annexin-V FITC and
Propidium Iodide. The results reveal a future path towards a wireless implanted LED-based device that can trigger photodynamic immunogenic cell death in deep-seated cancerous tissue.